ABSTRACT: Adults with inactive Crohn disease have been shown to have normal rates of protein turnover when compared with healthy adults. It is not known whether this is true for adolescents with inactive Crohn disease, when rate of protein synthesis must be greater than that of breakdown for normal development. The objective of this study was to determine whether enteral nutrition acutely suppresses proteolysis and increases protein synthesis in adolescents with inactive Crohn disease. Six adolescents (five males/one female; mean age, 15.8 Ϯ 1.9 y; range, 13.2-17.6 y; mean bone age, 14.6 Ϯ 1.8 y; range, 12.5-17 y) participated. Leucine (Leu) and phenylalanine (Phe) kinetics were measured using stable isotopes under fasted and fed conditions during a single study visit. In response to enteral nutrition, the endogenous rates of appearance (R a ) of Leu and Phe (reflecting proteolysis) decreased significantly by 40%. The percentages of splanchnic uptake of Leu and Phe were 35 Ϯ 10% and 13 Ϯ 12%, respectively. Under fed conditions, utilization of Phe for protein synthesis increased significantly. We conclude that in clinically stable adolescents with Crohn disease, enteral nutrition promotes anabolism by suppressing proteolysis and increasing protein synthesis. Rates of suppression of proteolysis were similar to those reported previously in normal children
